Modern circuity systems, for instance System on Chips (SoC), typically includes multiple power supplies for various purposes. Examples can be power supplies for digital core circuitry, memory circuitry, digital I/O circuitry and analog circuitry. Each of these power supplies may employ a voltage regulator, having as input a voltage reference. With the increasing attention to power dissipation, coming from the on-going miniaturization of electronic circuitries and devices, SoC design typically requires optimization of the power supplies of each particular circuitry block in order to reduce power consumption without affecting functionality. It is therefore typically advantageous to have different operating voltages for the digital core circuitry, memory circuitry, digital I/O circuitry and analog circuitry. Additionally, techniques such as Dynamic Voltage Scaling (DVS) is becoming increasingly interesting in this context as it allows to change the voltage supply depending on the needs. So, modern circuitry systems typically require the generation of multiple voltage references which also may be time-varying voltage references.
It is desirable that the generation of voltage references should be power efficient. Also considering that the voltage references may need to be active also during sleep modes, for instance for the purpose of enabling wake up of the system and maintaining relevant data in the memory. The power budget for generating voltage references may therefore be as small as few tens or hundreds of nA.
A prior art solution is to use switched-capacitor amplifiers. In this case, low power consumption can be achieved by choosing a very short switching period and by turning the amplifier off for the most of time, i.e. employing a small duty cycle.